The present invention relates generally to electrical solenoids, and more particularly to retaining apparatus of solenoids and methods of manufacturing solenoids.
Solenoids are widely used in the electromechanical and fluid controls industries, such as in engines and turbines, to switch a wide variety of control apparatus such as valves, drives, flow control devices, switches and the like between two states (typically either xe2x80x9conxe2x80x9d and xe2x80x9coffxe2x80x9d states or xe2x80x9copenxe2x80x9d and xe2x80x9cclosedxe2x80x9d states). Solenoids typically comprise a lamination stack and a wire coil wound about the lamination stack. The lamination stack and wire coil are housed and supported inside a solenoid housing that in turn can be mounted to the control apparatus.
Heretofore, the method of assembling and mounting the lamination stack and wire coil into a housing has been by potting the lamination stack and wire coil into the housing with a potting compound. According to this prior method of assembly, the lamination stack and wire coil are arranged in a fixed position inside the housing with leads of the wire coil connected to terminals on the housing. Then, potting compound (which is typically a relatively viscous liquid) is filled into all of voids between the housing, the lamination stack and wire coil. Thereafter, the potting compound is cured with high temperature baking over a predetermined time which solidifies the potting compound into a rigid solid mass and fixes the lamination stack and wire coil in position. Thereafter, the exposed end of the lamination stack and/or housing end are machine ground with a grinder to be coplanar with each other so that the solenoid seats in flat mating contact when mounted to fluid control devices or other such apparatus.
As will be appreciated by those of skill in the art, commercial production of solenoids using the potting method requires high volume production to justify all of the set up, tooling and fixture expenses. Minor changes to an existing solenoid design to meet different customer or application requirements are costly. Heretofore, there has been a desire for a lower volume or xe2x80x9cmedium volumexe2x80x9d production solenoids in the marketplace.
Furthermore, as will be more fully appreciated by the present invention, the extra step of grinding the end of the lamination stack and/or housing end has been found by the inventors of the present invention to be inefficient. The time and heat required for potting and curing the potting compound have also been found by the inventors to be inefficient. Furthermore, cured potting compound can shrink or crack over time which can limit solenoid life.
According to one aspect of the invention, it is an objective of the present invention to provide a less expensive method for commercially manufacturing and assembling a solenoid in medium volume production for the fluid controls industries or other industries where such solenoids are utilized.
According to a different aspect of the invention, it is another objective of the present invention to provide a solenoid that avoids the potential drawbacks associated with potting compound such as inefficiencies associated with potting steps and shrinkage of cured potting material over time.
It is another objective of the present invention to provide a method of manufacturing and assembling a solenoid that may avoid the step of grinding the final lamination stack and housing assembly.
It is a further object of the present invention to provide a solenoid capable of being adequately sealed for such applications that require sealing, while achieving any or all of the above objectives.
In accordance with the foregoing objectives and/or other such objectives, the present invention is directed toward an electrical solenoid suitable for fluid controls applications with a novel method and apparatus for retaining the lamination stack in a solenoid housing. Accordingly, an elastomeric retaining device of an elastomeric material is arranged between the housing and the lamination stack to perform the retaining function. An advantage of the elastomeric retaining device is that the need for potting compound and the steps of filling the housing with potting and curing the potting compound can be eliminated. As is the case in any solenoid, a wire coil is wound about the lamination stack in which the wire coil has an electrical connection extending through the housing for electrical communication with an external electrical control. As will be pointed out further below, however, there are also novel and beneficial aspects of the wire coil assembly of the disclosed embodiment.
It is an aspect of the present invention that the end of the lamination stack projects out of the housing slightly after manufacturing and assembly operations. When the solenoid is mounted, the end of the lamination stack retracts to be coplanar with the mounting surface of the housing causing the elastomeric retaining device to compress, and the elastomeric retaining device biases the lamination stack against the mounting surface for axial retention.
Other objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.